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Q173244: FIX: FindIndex Works Incorrectly When nIndex Is Negative

Article: Q173244
Product(s): Microsoft C Compiler
Version(s): winnt:2.0,2.1,2.2,4.0,4.1,4.2,5.0
Operating System(s): 
Keyword(s): kbnokeyword kbMFC kbVC200bug kbVC210bug kbVC220bug kbVC400bug kbVC410bug kbVC420bug kbV
Last Modified: 17-JUL-2001

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The information in this article applies to:

- The Microsoft Foundation Classes (MFC), used with:
   - Microsoft Visual C++, 32-bit Editions, versions 2.0, 2.1, 2.2, 4.0, 4.1 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2 
   - Microsoft Visual C++, 32-bit Professional Edition, version 4.2 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0 
   - Microsoft Visual C++, 32-bit Professional Edition, version 5.0 
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SYMPTOMS
========

If a value less than 0 is passed to the FindIndex function, the function will
ASSERT in debug mode and enter an infinite loop in release mode.

CAUSE
=====

The problem is that an ASSERT statement is used to test for a negative value in
the FindIndex function instead of an if...then statement that would return NULL
if the value is negative.

RESOLUTION
==========

Check the value that is passed to FindIndex to make sure that it is not negative
before calling the FindIndex function.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This problem was corrected in Visual C++ version 6.0.

MORE INFORMATION
================

The documentation for the FindIndex function in the CList, CStringList,
CPtrList, and CObList classes states that the return value is NULL if nIndex is
negative or too large.

In release mode, the program may also generate the following application error:

  

  The instruction at 0x... referenced memory at "0x00000000".
  
  The memory could not be "read".

REFERENCES
==========

See AFXTEMPL.H for CList, LIST_S.cpp for CStringList, LIST_P.cpp for CPtrList,
and LIST_O.cpp for CObList implementation details. The header file can be found
in the in the ...\VC\mfc\include directory and the source files can be found in
the ...\VC\mfc\src directory.

Additional query words:

======================================================================
Keywords          : kbnokeyword kbMFC kbVC200bug kbVC210bug kbVC220bug kbVC400bug kbVC410bug kbVC420bug kbVC500bug kbVC600fix kbGrpDSMFCATL kbNoUpdate 
Technology        : kbAudDeveloper kbMFC
Version           : winnt:2.0,2.1,2.2,4.0,4.1,4.2,5.0
Issue type        : kbbug
Solution Type     : kbfix

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